Berowne said:
The Leica-M 35/1.4 Asph has also a concave front element. Floating elements with AF will not work.
Andy
Yes, there is a smallish number of (old) WIDE-ANGLE lenses with retrofocus design and concave front element. But not for lenses with focal lengths of 50 or 58mm.
Zeiss has moved grom Planar design to Distagon with the new Milvus 50mm/1.4. And now this Canon patent ... Will be interesting to see whether it ever hors into production and if so, what performance it really will have.
AF is possible with floating element design. Canon EF 50/1.2 and 85/1.2 are living proof ... or the new Zeiss Batis 85/1.8 (which uses a conventional 1930s Sonnar design, with convex front element).